1. Field of the Invention
The invention relates to rectifying devices, and, more particularly, to a rectifying device which permits a current to flow in favor of one direction when driven by an AC input voltage and to an in-phase gate-boosting rectifier (IGR) which converts an AC input voltage to an output DC current based on the rectifying device.
2. Description of Related Art
In the application of RF-to-DC rectifiers, the dimensions of antenna can be reduced by increasing operating frequency. However, as the frequency increases, the sensitivity of the rectifiers drops quickly because the parasitic capacitance from the passive and the active devices starts to dominate.
In order to improve the high-frequency performance of the rectifiers, a diode with reduced forward voltage drop and reverse leakage current is desired to improve sensitivity. In some approaches, a two-terminal diode can be implemented using a diode-connected MOSFET, and the forward voltage drops can be reduced by reducing the rectifying a threshold voltage of a transistor. However, due to the threshold voltage issue, the output current of the transistor diode will be generated only when an instantaneous Vin is greater than the MOSFET threshold voltage Vth, which greatly influences the sensitivity.
Although the threshold voltage Vth can be reduced by providing a gate bias voltage, a large bias voltage not only reduces effective threshold voltage, but also increases reverse leakage current. Moreover, since all internal voltages are initially zero, the input voltage swing still needs to be higher than the threshold voltage Vth for starting up.
In order to generate a larger MOSFET gate voltage swing from the input voltage swing, an inductive peaking method has been proposed. The inductive peaking method approach utilizes an inductor to generate a larger gate voltage swing, so as to address to the starting up issue. However, in this method the gate-source voltage VGS and drain-source voltage VDS are not in phase, such that excessive reverse leakage current will be generated. Also, the input impedance of the rectifier is low due to a series gate inductor and gate capacitor resonant circuit, and such low resonant impedance will shunt between drain and source and reduce the voltage swing of VDS.
From the foregoing, how to find a way to provide a diode with reduced forward voltage drop and reverse leakage current becomes the objective being pursued by persons skilled in the art.